Euler's goniometers or cradles are standard devices in X-ray and neutron diffractometry, especially for single-crystal diffraction. In general, a two-circle Euler's cradle or goniometer provides a specimen holder rotatable about two turning circles (i.e. in two mutually perpendicular planes, namely the phi-circle and the chi-circle) for determining the structure of a crystal whereby the rotational movement in each plane is provided generally by respective stepper motors.
Examinations of crystal structure have turned out to be especially interesting at low or cryogenic temperatures so that low-temperature devices have been developed for this purpose.
Consequently, Euler goniometers of considerable size are known in which a crystat for cooling the test samples, in particular by using liquid helium, is mounted on the phi-circle and is swingable through a given, usually limited angle.
Such Euler goniometers, however, have proven to be too bulky and, in particular, provide rotational possibilities only within a very limited angle range.